Attic ventilation has improved significantly over time. Many types of attic vents are used for attic ventilation such as, for instance, attic fans, attic vents, and gable vents. One type of attic vent that has proven successful, particularly for gable roofs with one or more roof ridges, is the ridge vent. Ridge vents are available in many configurations. Generally, however, a ridge vent covers an open ridge slot along the apex or ridge of a gable roof. The ridge vent is configured to define a flow path for hot and/or humid attic air to exit the attic through the ridge slot and ridge vent, while preventing rainwater, snow, and insects from entering the attic. Ridge vents may be configured, for example, as an open weave mat material that is applied over the ridge slot and covered with ridge cap shingles. Cobra® ridge vent available from GAF Materials Corporation of Wayne, NJ is an example of such a ridge vent. Other ridge vents are configured with a flexible central panel that overlies the ridge slot and conforms to the shape of the ridge. The panel is spaced from the roof deck and vents are defined along the outboard edges of the panel. Hot attic air flows by convection through the ridge slot, through the space between the panel and the roof deck, and is expelled through the vents. This type of ridge vent may or may not be covered with ridge cap shingles. In general, ridge vents of all types are coupled with soffit or eave vents that compliment in net free ventilating area that of the ridge vents so that hot air exiting through the ridge vent is replaced by cool ambient air drawn in through the soffit or eave vents.
Ridge vents are efficient attic ventilators when the air in the attic is sufficiently hot to drive robust convection. There are times, however, when this is not the case, but it nevertheless is desirable that the attic be fully ventilated. For example, the temperature of the attic air may be too low to drive robust ventilation, but the humidity in the attic may be undesirably high such that attic ventilation is needed anyway. Under these and other circumstances, some other mechanism for expelling air out of the attic and drawing in fresh air through the soffit or eave vents is required. It has been proposed to mount a powered fan or blower beneath a section or sections of a ridge vent to force attic air through the ridge vent and out of the attic. Several configurations of this proposal are extant. However, most have inherent shortcomings such as expense, difficulty of installation, requirement for a specially designed ridge vent, or inapplicability to roofs with a central ridge beam along the ridge. Accordingly, there remains a need for a powered forced air ventilation system for use with ridge vents that, among other things, is easily installed by common roofers or carpenters, that operates efficiently and provides superior air flow in cubic feet per minute (Cfm), that consumes minimum electrical power, that may be installed in roofs with or without central ridge beams, and that is reliable and affordable as a roofing accessory. It is to the provision of such a powered ventilation system that the present disclosure is primarily directed.